Radiation clinical thermometer

ABSTRACT

A radiation clinical thermometer includes a probe, a detection signal processing section, a body temperature operating section, and a display unit. A filter correction section for setting a correction value based on the transmission wavelength characteristics of a filter is arranged. The body temperature operating section receives infrared data, temperature-sensitive data, and the correction value from the filter correction section so as to calculate body temperature data.

.Iadd.

This is a continuation of application Ser. No. 07/605,589, filed Oct.29, 1990, now abandoned, which is a reissue of application Ser. No.07/335,616, filed Jul. 10, 1989, now U.S. Pat. No. 4,932,789. .Iaddend.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a portable, compact radiation clinicalthermometer for measuring a temperature upon insertion in an externalear canal.

2. Description of the Prior Art

Recently, a pen type electronic clinical thermometer has been widelyused in place of a glass clinical thermometer.

This electronic clinical thermometer is not fragile, can perform adigital display which is easy to read, and can generate an alarm soundsuch as a buzzer sound for signaling the end of temperature measurement.However, this clinical thermometer requires about 5 to 10 minutes fortemperature measurement, i.e., substantially the same length of time asthat required by a glass clinical thermometer. This makes a user feelthat body temperature measurement is cumbersome. Such a long measurementtime is based on a method of inserting a sensor portion in an armpit ora mouth and bringing it into contact with a portion to be measured. Ameasurement time is prolonged due to the following two reasons:

(1) A skin temperature at an armpit or a mucous membrane temperature ina mouth is not equal to a body temperature prior to temperaturemeasurement, and gradually reaches the body temperature after the armpitor the mouth is closed.

(2) Since the sensor portion of the clinical thermometer has been cooleddown to an ambient temperature, when it is inserted in a portion to bemeasured, the temperature of the portion is further lowered.

Temperature measurement of a conventional clinical thermometer will bedescribed with refence to FIG. 1.

FIG. 1 shows temperature measurement curves of a contact type electronicclinical temperature. In FIG. 1, temperature measurement time is plottedalong the axis of abscissa and measurement temperatures are plottedalong the axis of ordinate. A curve H represents a temperature curve ofan armpit as a portion to be measured; and a curve M, a measurementtemperature curve obtained by the clinical thermometer. Accordingly, theskin temperature of the armpit is 36° C. or less at measurement starttime t₁, and the temperature of a clinical thermometer sensor portion iscooled to 30° C. or less. When the sensor portion is inserted in thearmpit in this state, and the armpit is closed, the measurementtemperature represented by the curve M of the sensor portion is quicklyraised. However, the temperature represented by the curve H of thearmpit begins to rise gradually toward an actual body temperature T_(b)after it is cooled by the sensor portion to a temperature at time t₂.The two temperature curves H and M coincidentally rise from time t₃ whenthe sensor portion is warmed to the skin temperature of the armpit. Asdescribed above, however, it takes about 5 to 10 minutes for the curveto reach the actual body temperature. As is known, a method of measuringa body temperature is performed in practice as follows. Measurement isperformed from time t₁ at predetermined intervals. The measurementvalues are compared with each other, and maximum values are sequentiallystored. At the same time, a difference between the measurement values issequentially checked. The instant when the difference becomes smallerthan a predetermined value is set at time t₄, and the temperaturemeasurement is stopped. Thus, the greatest value at this time isdisplayed as a body temperature e.g., Japanese Patent Laid-Open (Kokai)No. 50-31888).

In consideration of the above-described reasons (1) and (2), conditionsfor performing body temperature measurement within a short period oftime are: selection of a portion having a body temperature prior tomeasurement, and an actual measurement without bringing a cooled sensorportion into contact with the portion to be measured.

A drum membrane is, therefore, selected as a portion having a bodytemperature prior to measurement, and a radiation clinical thermometeris proposed as a clinical thermometer for measuring the temperature ofthe portion in a nontact manner (e.g., U.S. Pat. No. 3,282,106).

The principle of a radiation thermometer on which the above radiationclinical thermometer is based will be described below.

A radiation thermometer is based on a law of physics, i.e., "all objectsemit infrared radiation from their surfaces, and the infrared radiationamounts and the spectral characteristics of the objects are determinedby their absolute temperatures as well as their properties and states oftheir finished surfaces." This law will be described with reference tothe following laws.

The Planck's law states a relationship between the radiant intensity,spectral distribution, and temperature of a blackbody as follows:

    W(λ,T)═2πc.sup.2 h/λ.sup.5 (e.sup.hc/k λT -1).sup.-1                                                ( 1)

where

W (λ,T): spectral radiant emittance [W/cm². μm]

T: absolute temperature of blackbody [K]

λ: wavelength of radiation [μm]

c: velocity of light═2.998×10¹⁰ [cm/sec]

h: Planck's constant═6.625×10⁻³⁴ [W.sec^(2])

k: Boltzmann constant═1.380×10²³ [W.sec/K]

FIG. 3 shows the Planck's law. As is apparent from FIG. 3, as thetemperature of the blackbody rises, the radiation energy is increased.In addition, the radiation energy varies depending on wavelengths. Thepeak value of the radiant emittance distribution shifts to the shortwavelength side with an increase in temperature, and the radiationoccurs over a wide wavelength band.

Total energy radiated from the blackbody can be obtained by integratingW(λ, T) given by equation (1) with respect to λ from λ═0 to λ═∞. This isthe Stefan-Boltzmann law. ##EQU1##

W₁ : total energy radiated from blackbody [W/cm² ]σ: Stefan-Boltzmannconstant═5.673×10¹² [W/cm²..deg⁴ ]

As is apparent from equation (2), the total radiation energy W₁ isproportional to a power of four of the absolute temperature of theblackbody light source. Note that equation (2) is obtained byintegrating the infrared radiation emitted from the blackbody withrespect to all the wavelengths.

All the above-described laws are derived from the blackbody having anemissivity of 1.00. In practice, however, most objects are not idealradiators, and hence have emissivities smaller than 1.00. For thisreason the value obtained by equation (2) must be corrected bymultiplying a proper emissivity. Radiation energy of most objects otherthan the blackbody can be represented by equation (3): ##EQU2##

ε: emissivity of object

Equation (3) represents infrared energy which is radiated from an objectand incident on an infrared sensor. However, the infrared sensor itselfemits infrared radiation in accordance with the same law describedabove. Therefore, if the temperature of the infrared sensor itself isT₀, its infrared radiation energy can be given as σT₀ ⁴, and energy Wobtained by subtracting radiation energy from incident energy is givenby equation (4):

    W═σ(εT.sup.4 +γT.sub.a.sup.4 -T.sub.0.sup.4) (4)

T_(a) : ambient temperature of object

γ: reflectance of object

Since the transmittance of the object to be measured can be regarded aszero, γ═1-ε can be established.

In equation (4), the infrared sensor is considered to be ideal and hencehas an emissivity of 1.00.

In addition, assuming that the infrared sensor is left in an atmosphereof an ambient temperature T_(a) so that the infrared sensor temperatureT₀ is equal to the ambient temperature T_(a), equations (4) can berewritten as equation (5): ##EQU3##

FIG. 2 shows a basic arrangement of a conventional radiationthermometer. The arrangement will be described below with reference toFIG. 2.

A radiation thermometer comprises an optical system 2, a detectingsection 3, an amplifying section 4, an operating section 5, and adisplay unit 6.

The optical system 2 is constituted by a focusing means 2a forefficiently focusing infrared radiation from an object L to be measured,and a filter 2b having transmission wavelength characteristics. Acylindrical member having an inner surface plated with gold is used asthe focusing means 2a. A silicon filter is used as a filter 2b.

The detecting section 3 is constituted by an infrared sensor 3a and atemperature-sensitive sensor 3b. The infrared sensor 3a convertsinfrared radiation energy obtained by subtacting its own radiationenergy from incident infrared radiation energy focused by the opticalsystem 2 into an electrical signal, i.e., an infrared voltage v_(s). Inaddition, the temperature-sensitive sensor 3b is arranged near theinfrared sensor 3a to measure the temperature of the infrared sensor 3aand its ambient temperature T₀, and outputs a temperature-sensitivevoltage v_(t). A thermopile and a diode are respectively used as theinfrared sensor 3a and the temperature-sensitive sensor 3b.

The amplifying section 4 comprises an infrared amplifier 4a, constitutedby an amplifying circuit and an A/D converter for converting an outputvoltage from the amplifying circuit into digital infrared data V_(d),for amplifying the infrared voltage v_(s) output from the thermopile,and a temperature-sensitive amplifier 4b, constituted by an amplifyingcircuit and an A/D converter for converting an output voltage from theamplifying circuit into digital temperature-sensitive data, foramplifying the temperature-sensitive voltage v_(t) as a forward-biasedvoltage from the temperature-sensitive sensor 3b, i.e., the diode.

Two signals V_(d) and T₀ from the amplifying section 4 are thenconverted into temperature data T, and are displayed on the display unit6. The operating section 5 comprises an emissivity input means 5a forsetting an emissivity ε of the object L, and an operating circuit 5c forperforming an operation based on equation (5).

With the above-described arrangement, temperature measurement of theobject L can be performed by a noncontact scheme. An operation of thistemperature measurement will be described below.

The object L emits infrared radiation, and its wavelength spectrumdistribution covers a wide wavelength range, as shown in FIG. 3. Theinfrared radiation is focused by the focusing means 2a, transmittedthrough the filter 2b having the transmission wavelengthcharacteristics, and reaches the infrared sensor 3a.

Other infrared radiation energies reach the infrared sensor 3a. One isinfrared radiation energy emitted from a certain object near the objectL, which is reflected by the object L and is then transmitted throughthe filter 2b and reaches the infrared radiation energy. Another isinfrared radiation energy emitted from the infrared sensor 3a or acertain object near the sensor 3a, which is reflected by the filter 2band reaches the sensor 3a. Still another is infrared radiation enengywhich is emitted from the filter 2b and reaches the sensor 3a.

The infrared radiation energy from the infrared sensor 3a can berepresented by equation (3). In this case, ε═1.00. That is, to measurethe temperature of the infrared sensor 3a itself is to indirectlymeasure the infrared radiation energy from the infrared sensor 3a. Forthis purpose, the temperature-sensitive sensor 3b is arranged near theinfrared sensor 3a and measures the temperature of the infrared sensor3a and the ambient temperature T₀. The infrared sensor 3a converts theinfrared radiation energy W obtained by subtracting infrared radiationenergy emitted therefrom from infrared radiation energy incident thereoninto an electrical signal. Since the infrared sensor 3a employs athermopile, it outputs the infrared voltage v_(s) proportional to theinfrared radiation energy W.

In this case, the infrared voltage v_(s) as an output voltage from theinfrared sensor 3a corresponds to a value obtained by multiplying theproduct of the infrared radiation energy W per unit area and alight-receiving area S of the infrared sensor 3a by a sensitivity R. Theinfrared data V_(d) as an output voltage from the infrared amplifier 4acorresponds to a value obtained by multiplying the infrared voltagev_(s) from the infrared sensor 3a by a gain A of the infrared amplifier4a.

    V.sub.s ═R.W.S

    V.sub.d ═A.v.sub.s

Since the above equations can be established, equation (5) can beexpressed as equation (6) as follows:

    V.sub.d ═ε.σSRA(T.sup.4 -T.sub.0.sup.4)  (6)

where

V_(d) : output voltage from infrared amplifier 4a

S: light-receiving area of infrared sensor 3a

R: sensitivity of infrared sensor

A: gain of infrared amplifier 4a

Generally, equation (6) is simplified by setting K₁ ═σSRA, and hence thetemperature T of the object L is calculated according to equation (7).##EQU4##

A thermal infrared sensor used for a conventional radiation thermometerhas no wavelength dependency. However, a transmission member such as asilicon or quarts filter is arranged as a window member on the frontsurface of a can/package in which the infrared sensor is mounted due tothe following reason. Since infrared radiation from an object has thewavelength spectrum distribution shown in FIG. 3, such a filter is usedto transmit only infrared radiation having a main wavelength bandtherethrough so as to reduce the influences of external light. Each ofthe above-described transmission members has unique transmissionwavelength characteristics. A proper transmission member is selected onthe basis of the temperature of an object to be measured, workabilityand cost of a transmission member and the like.

FIG. 4 shows the transmittance of a silicon filter as one of thetransmission members. The silicon filter shown in FIG. 4 transmits onlyinfrared radiation having a wavelength band from about 1 to 18 [μm]therethrough, and has a transmittance of about 54%.

As described above, an infrared sensor with a filter has wavelengthdependency, i.e., transmits infrared radiation having a specificwavelength band because of the filter as a window member although thesensor itself is a temperature sensor and has no wavelength dependency.

Therefore, equation (5) obtained by integrating infrared radiationenergy incident on the infrared sensor with a filter with respect to allthe wavelengths cannot be applied to the infrared sensor with a filterfor transmitting infrared radiation having a specific wavelength band,and an error is included accordingly.

Furthermore, in the conventional arrangement, the sensitivity R of theinfrared sensor is used as a constant. In practice, however, thesensitivity R of the infrared sensor varies depending on the infraredsensor temperature T₀. FIG. 5 shows this state. In FIG. 5, thesensitivity R is obtained by actually measuring the output voltage v_(s)from a thermopile as an infrared sensor by using a blackbody, and theinfrared sensor temperature T₀ is changed to plot changes in sensitivityR at the respective temperatures. As a result, it is found that thetemperature dependency of the sensitivity R can be approximated to astraight line as represented by equation (8):

    R═a {1-β(T.sub.0 -T.sub.m)}                       (8)

where a is the sensitivity R as a reference when T₀ ═T_(m),, T_(m) is arepresentative infrared sensor temperature, e.g., an infrared sensortemperature measured in a factory, and β represents a coefficient ofvariation, In this case, a coefficient of variability per 1 [deg] is-0.3 [%/deg]. The variation in sensitivity R described above inevitablybecomes an error.

The coefficient of variation β is influenced by the manufacturingconditions of a thermopile, and can be decreased by increasing thepurity and process precision of the thermopile. However, thermopiles onthe market which are mass-produced have the above value.

A radiation thermometer, however, is normally designed to measure hightemperatures, and has a measurement range from about 0° to 300° C. andmeasurement precision of about ±2° to 3° C. Therefore, errors due to theabove-described filter characteristics, variations in sensitivity of aninfrared sensor, and the like are neglected, and hence no countermeasurehas been taken so far. When measurement conditions as a clinicalthermometer are taken into consideration, however, a temperaturemeasurement range may be set to be as small as about 33° C. to 43° C.,but ±0.1° C. is required for temperature measurement precision.Therefore, if the above-described radiation thermometer is used as aclincial thermometer, temperature measurement precision must beincreased by taking countermeasures against errors due to the filtercharacteristics and the variations in sensitivity of infrared radiation.

A radiation clinical thermometer disclosed in U.S. Pat. No. 4,602,642employs the following system as a countermeasure.

This radiation clinical thermometer comprises three units, i.e., a probeunit having an infrared sensor, a chopper unit having a target, and acharging unit. In addition, a heating control means for preheating theinfrared sensor and the target to a reference temperature (36.5° C.) ofthe external ear canal is provided, and is driven by charged energy fromthe charging unit. When a body temperature is to measured, the probeunit is set in the chopper unit, and the probe unit having the infraredsensor and the target are preheated by the heating control means. Inthis state, calibration is performed. Thereafter, the probe unit isdetached from the chopper unit and is inserted in an external ear canalto detect infrared radiation from a drum membrane. A body temperaturemeasurement is performed by comparing the detected infrared radiationwith that from the target.

Temperature measurement precision is increased by the above-describedsystem for the reasons to be described below.

According to this system, various error factors are eliminated bypreheating the probe unit having the infrared sensor and the target to areference temperature (36.5° C.) close to a normal body temperature byusing the heating control means. That is, by heating the probe to thereference temperature higher than a room temperature and keeping theinfrared sensor at a constant temperature regardless of ambienttemperatures, sensitivity variations of the infrared sensor can beeliminated, and hence its error can be neglected. In addition,calibration is performed so as to set the reference temperature of thetarget to be close to a body temperature to be measured, and acomparative measurement is then performed so that errors and the likedue to the filter characteristics are reduced to a negligible level.Furthermore, since the probe is preheated to a temperature close to abody temperature, the problem of the conventional measurement system canbe solved, i.e., the problem that when a cool probe is inserted in anexternal ear canal, the temperatures of the external ear canal and thedrum membrane are lowered because of the probe, so that correct bodytemperature measurement cannot be performed.

The above-described radiation clinical thermometer disclosed in U.S.Pat. No. 4,602,642 is excellent in temperature measurement precision.However, since this therometer requires a heating control unit with highcontrol precision, its structure and circuit arrangement becomecomplicated, thereby increasing the cost. In addition, it requires along stable period to preheat the probe and the target and control theirtemperatures to a predetermined temperature. Moreover, since the heatingcontrol unit is driven by a relatively large-power energy, a largecharging unit having a power source cord is required. Therefore, theabove-described system cannot be applied to a portable clinicalthermometer using a small battery as an energy source.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a portable, compactradition clinical thermometer at low cost while high temperaturemeasurement precision is maintained by solving the above-describedproblems.

According to an aspect of the present invention, a filter correctingmeans outputs a correction value based on the transmission wavelengthcharacteristics of a filter so that a body temperature is calculated onthe basis of infrared data, temperature-sensitive data, and the filtercorrection value.

According to another aspect of the present invention, a body temperatureis calculated on the basis of infrared data, temperature-sensitive data,a filter correction value, sensitivity data input from a sensitivitydata input means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing temperature measurement curves of aconventional electronic clinical thermometer;

FIG. 2 is a block diagram showing a circuit arrangement of theconventional electronic thermometer;

FIG. 3 is a graph showing changes in intensity of an infrared wavelengthspectrum depending on the temperature of an object;

FIG. 4 is a graph showing the transmission wavelength characteristics ofa silicon filter;

FIG. 5 is a graph showing the sensitivity characteristics of an infraredsensor;

FIG. 6 is block diagram showing a circuit arrangement of an electronicclinical thermometer according to an embodiment of the presentinvention;

FIG. 7 is a graph of temperature characteristics for explaining anapproximate expression of temperature measurement by the conventionalelectronic theremometer;

FIG. 8 is a plan view of an electronic thermometer of the presentinvention;

FIG 9 is a side view of the electronic thermometer in FIG. 8;

FIG. 10 is a sectional view showing an internal structure of atemperature measuring section of the electronic clinical thermometer inFIG. 8;

FIG. 11 is an enlarged sectional view showing part of the temperaturemeasuring section of the electronic clinical thermometer;

FIG. 12 a side view showing a state wherein the electronic clinicalthermometer is stored in a storage case;

FIG. 13 is a view showing a state wherein the temperature measuringsection of the electronic clinical thermometer is inserted in anexternal ear canal;

FIG 14 is a block diagram showing a circuit arrangement of an electronicclinical thermometer according to a second embodiment of the presentinvention;

FIG. 15 is a flow chart for explaining a body temperature calculatingoperation in the embodiment shown in FIG. 14;

FIG. 16 is a graph showing a temperature measurement curve of theelectronic clinical thermometer of the present invention;

FIG. 17 is a circuit diagram of a peak hold circuit in the embodimentshown in FIG. 14;

FIG. 18 is a sectional view showing an internal structure of atemperature measuring section of an electronic clinical thermometeraccording to a third embodiment of the present invention;

FIG. 19 is a block diagram showing a circuit arrangement of theelectronic clinical thermometer according to the third embodiment of thepresent invention; and

FIG. 20 is a sectional view showing an internal structure of amodification of the temperature measuring section of the electronicclinical thermometer according to the third embodiment of the presentinvention shown in FIG. 18.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described below with reference to theaccompanying drawings.

FIG. 6 is a block diagram showing a basic circuit arrangement of aradiation clinical thermometer according to a first embodiment of thepresent invention.

In this embodiment, variations in sensitivity R are reduced to anegligible level by using a thermopile manufactured under goodmanufacturing conditions so as to correct filter characteristics.

The same reference numerals in FIG. 6 denote the same parts as in FIG.2, and a description thereof will be omitted.

The radiation clinical thermometer of this embodiment differs from thatshown in FIG. 2 in measurement of the temperature of the drum membraneof an ear as an object to be measured and the arrangement of anoperation section 5.

The operation section 5 of a radiation clinical thermometer 70 comprisesan emissivity input means 5a for setting an emissivity ε of an object Lto be measured, a filter correction means 5b for setting transmissionwavelength characteristics of a filter 2b, and a body temperatureoperating circuit 5c.

The operating section 5 of this embodiment, therefore, calculates ameasurement body temperature T_(b) on the basis of an emissivity setvalue from the emissivity input means and a filter correction value fromthe filter correcting means 5b.

An equation for temperature calculation with consideration of thewavelength dependency of an infrared sensor with a filter will bedescribed below.

As described above, the infrared sensor 3a converts the infraredradiation energy W obtained by subtracting radiation energy fromincidence energy into the infrared voltage v_(s). The energy W can begiven by equation (9): ##EQU5## where η(λ) is the transmittance of thefilter.

The first term of equation (9) represents infrared radiation energyemitted from the object L having the emissivity ε which is transmittedthrough the filter 2b and reaches the sensor 3a. The second termrepresents infrared radiation energy emitted from emitted from an objectlocated near the object L and having the temperature T₀, which istransmitted through the filter 2b and reaches the sensor 3a. The thirdterm represents infrared radiation energy emitted from the infraredsensor 3a having the temperature T₀ or an object located near the sensor3a, which is reflected by the filter 2b and reaches the sensor 3a, orinfrared radiation energy which is emitted from the filter 2b having thetemperature T₀ and reaches the sensor 3a. In this case, the sum of thetransmittance, reflectance, and emissivity of the transmission member isequal to one. The third term is established in consideration of thereflection or radiation by the filter 2b. Note that the infraredradiation from the infrared sensor 3a is reflected by the filter 2b. Thefourth term represents infrared radiation energy from the infraredsensor 3a itself having the temperature T₀, and a sign of this term isnegative.

Equation (9) can be rewritten to equation (10) as follows: ##EQU6##

It is found, therefore, that the infrared radiation energy obtained bysubtracting radiation energy from incident energy of the infrared sensor3a having the filter 2b does not correspond to "a value proportional tothe difference between a power of four of the absolute temperature andthat of the temperature of the sensor itself" as represented by equation(5), but must be given by an equation based on the transmissionwavelength characteristics of the filter 2b as represented by equation(10). That is, a new equation must be established in place of theStefan-Boltzmann law represented by equation (2).

If infrared radiation energy emitted from the blackbody having theabsolute temperature T, which is transmitted through a filter having atransmittance η(λ) is set to be F(T),F(T) can be represented by equation(11) as follows: ##EQU7##

In this case, assuming that the absolute temperature T has a temperaturerange from T_(min) to T_(max), the infrared radiation energy F(T) iscalculated with respect arbitrary absolute temperatures T₁, T₂, T₃, . .. , T_(n) according to equation (11). The calculation results aresummarized in Table 1.

                  TABLE 1                                                         ______________________________________                                                T   F(T)                                                              ______________________________________                                                T.sub.1                                                                           F(T.sub.1)                                                                T.sub.2                                                                           F(T.sub.2)                                                                T.sub.3                                                                           F(T.sub.3)                                                                .   .                                                                         .   .                                                                         .   .                                                                         T.sub.n                                                                           F(T.sub.n)                                                        ______________________________________                                    

It is, therefore, seen how the relationship between the absolutetemperature T and the infrared radiation energy F(T) transmitted throughthe filter is associated with the Stefan-Boltzmann law. FIG. 7 is agraph for explaining the examination process. The process will bedescribed below with reference to FIG. 7.

In this graph, absolute temperatures [K] are plotted along the axis ofabscissa and radiation energies [W/cm² ] are plotted along the axis ofordinate. Referring to FIG. 7, a curve A is a characteristic curve basedon equation (2) representing the Stefan-Boltzmann law, and a curve B isa characteristic curve based on the present invention considering thefilter characteristics.

The curve B is obtained such that a curve B' is prepared by connectingpoints respectively representing radiation energies at the absolutetemperatures T₁ to T_(n) shown in Table 1. and the curve A is modifiedand moved to overlap the curve B'. Types of modification and movement ofthe curve A' are determined by selecting a coefficient a of a term ofdegree 4 of the curve A, a displacement b in the direction of theabscissa axis, and a displacement c in the direction of the ordinateaxis so as to overlap the curve A and the curve B'.

As a result, equation (11) is approximated to equation (12) by using thethree types of set values a, b, and c.

    F(T)═a.(T-b).sup.4 +c                                  (12)

Subsequently, proper values a, b, and c in equation (12) are obtainedfrom the values shown in Table 1 by a method of least squares or thelike. Substitutions of these values into equation (12) yield anapproximate equation.

The set values a, b, and c will be described below in comparison withequation (2) representing the Stefan-Boltzmann law.

The set value a is a coefficient of the absolute temperature T of degree4, and corresponds to the Stefan-Boltzmann constant σ of the curve A.The value a takes a unit value of [W/cm² deg⁴ ]. The set value brepresents a symmetrical axis temperature. In the curve A, an absolutetemperature 0 [K] is set to a symmetrical axis, whereas in the curve B,an absolute temperature b [K] is set to be a symmetrical axis.

The set value c represents a minimum value. In the curve A, 0 [W/cm² ]is set to be an offset, whereas in the curve B, c [W/cm² ] is set to bean offset.

If equation (10) is rewritten by using equation (12), equation (13) isestablished as follows: ##EQU8##

As is apparent from equation (13), the minimum value c is canceled.

In this case, the infrared data V_(d) based on infrared radiationemitted from the drum membrane is obtained from the light-receiving areaS and the sensitivity R of the infrared sensor 3a and the gain A of theinfrared amplifier 4a by setting K₂ ═aSRA.Equation (13) is thenrewritten as equation (14). The body temperature T_(b) through the drummembrane is calculated by using equation (15) on the basis of equation(14). ##EQU9##

That is, when a filter having transmission wavelength characteristics isused for an optical system member, a temperature calculation is notperformed on the basis of the law "infrared radiation energy isproportional to a power of four of the absolute temperature T", but mustbe based on equation (14) representing the law "Infrared radiationenergy is proportional to a power of four of (the absolute temperatureT- the symmetrical axis temperature b)."

As a result, the filter correcting means 5b shown in FIG. 6 outputs thesymmetrical axis temperature b, and the operating circuit 5c calculatesthe body temperature T_(b) of the object L to be measured, i.e., thedrum membrane on the basis of equation (15).

An approximate expression in consideration of a silicon filter used asthe filter 2b in practice will be described below.

FIG. 4 shows the transmission wavelength characteristics of the siliconfilter. However, in order to simplify a calculation, the transmissionwavelength band of the silicon filter is set to be 1 to 18 [μm], and itstransmittance is set to be 54%. ##EQU10##

Equation (1) is substituted into W(λ, T).

Since a measurement environment, i.e., the measurement temperature rangeof the object to be measured is set between 0 [°C.] and 50 [°C.].T_(min) and T_(max) are respectively

set to be 273 [K] and 323 [K]. Table 2 shows the calculation results ofequation (16).

The values a, b, and c when equation (12) is approximated by using thedata shown in Table 2 are obtained by a method of least squares:

a═4.101×10⁻¹² [W/cm².deg⁴ ]

b═45.96[K]

c═-6.144×10⁴ [W/cm² ]

The coefficient a of a term of degree 4 and the symmetrical axis b thusobtained represent the transmission wavelength characteristics of thesilicon filter. These values a and b are output from the filtercorrecting means 5b. The filter correcting means 5b is part of anoperating program memory of the operating section 5, in whichcoefficient a of the term of degree 4 and the symmetrical axistemperature b are written.

                  TABLE 2                                                         ______________________________________                                        T      f(T) ×    T      f(T) ×                                    [K]    10.sup.-3 [W/cm.sup.2 ]                                                                       [K]    10.sup.-3 [W/cm.sup.2 ]                         ______________________________________                                        273    10.290          299    16.208                                          275    10.679          301    16.746                                          277    11.078          303    17.298                                          279    11.487          305    17.862                                          281    11.908          307    18.439                                          283    12.339          309    19.030                                          285    12.782          311    19.634                                          287    13.236          313    20.252                                          289    13.701          315    20.884                                          291    14.178          317    21.530                                          293    14.667          319    22.191                                          295    15.169          321    22.865                                          297    15.682          323    23.555                                          ______________________________________                                    

When a silicon filter is used as a window member for measurement of aninfrared sensor, the temperature T of an object to be measured is notcalculated by equation (5), but is calculated by equation (14), therebyperforming temperature calculations with high precision.

As is apparent from the above description, according to this embodiment,even if a transmission member having transmission wavelengthcharacteristics is used as a window member of an infrared sensor,temperature measurement of an object to be measured can be performedwith high precision.

In addition, even if the material of the transmission member as a windowmember of the infrared sensor is changed, temperature measurement can beperformed with high precision by updating the value of the filtercorrecting means 5b as part of the program memory.

In the above embodiment, an approximate expression having a term ofdegree 4 as represented by equation (12) is used as a new equationreplacing the Stefan-Boltzmann law. However, as shown in FIG. 13, inbody temperature measurement, only a portion of the temperaturemeasurement curve is used as a measurement range such as the range fromT_(min) ti T_(max) . Therefore, an approximate expression having a termof degree 4 need not be used. Satisfactory precision of a clinicalthermometer can be obtained by using an approximate expression with aproper degree. For example, expression (14) can be employed as anapproximate equation having a term of degree 2:

    V.sub.d ═εK.sub.2'{(T.sub.b -B').sup.2 -(T.sub.0 -b').sup.2 }(14')

A detailed arraangement of a radiation clinical thermometer which isactually manufctured by using a commercially available thermopilemanufactured in consideration of mass production will be described belowas a second embodiment of the present invention.

FIGS. 8 and 9 are bottom and side views, respectively, showing aradiation clinical thermometer according to the second embodiment of thepresent invention. Reference numberal 1 denotes a radiation clinical;thermometer comprising a main body portion 10 and a head portion 11. Thedisplay unit 6 for displaying a body measurement is arranged on thelower surface of the main body portion 10. A check button 12 having apush button structure is formed on the upper surface of the portion 11.A power switch 13 having a slide structure and major buttons 14 and 15each having a push button structure are respectively formed on the sidesurfaces of the portion 11.

The head portion 11 extend from the end of the main body portion 10 inthe form of an L shape. The end of the head portion 11 constitutes aprobe 16. The probe 16 comprises an optical system 2 and a detectingsection 3 shown in FIG. 6.

The radiation clinical theremometer 1 is operated as follows. A checkoperation (to be described later) is performed while the power switch isON. Thereafter, while the probe 16 is inserted in an external ear canalof a patient to be examined, either or both of the major switches 14 and15 is/are depressed, thereby instantaneously completing body temperaturemeasurement. The measurement result is displayed on the display unit 6as a body temperature.

FIG. 10 is a sectional view of the head portion 11. Each of case members17 and 18 consists of a resin molded member having a very low thermalconductivity. A portion of the case 17 covering the probe 16 constitutesa cylindrical member 17a, in which a metal housing 19 consisting of alightweight metal having a high thermal conductivity such as aluminum isfitted. The metal housisng 19 .Iadd.is integrally formed and.Iaddend.comprises a cylindrical portion 19a and a base portion 19dhaving a hollow portion 19b communicating with the cylindrical portion19a and a recess 19c in which a temperature-sensitive element isembedded. In addition, a step portion 19e for attachment of a filter isformed at the distal end of the cylindrical portion 19a. An opticalguide 20 consisting of a brass (Bu) pipe having an inner surface platedwith gold (Au) is fitted in the cylindrical portion 19a. A filter memberin the form of a dust-proof hard cap 21 selectively allowing infraredradiation to pass therethrough is fixed to the step portion 19e. Inaddition, a thermopile as the infrared sensor 3a and thetemperature-sensitive sensor 3b are respectively embedded in the hollowportion 19b and the recess 19c of the base portion 19d by sealing resins22 and 23. The infrared sensor 3a and the temperature-sensitive sensor3b are respectively connected to wiring patterns of a circuit board 26through leads 24 and 25, and are led to amplifying circuits to bedescribed later.

According to the above-described arrangement, since the infrared sensor3a, the optical guide 20, and the hard cap 21 are connected to eachother through the metal housing 19 having a high thermal conductivity,they can always be kept in a thermal equilibrium state. Thisuniform-temperature is detected by the temperature-sensitive sensor 3b.Reference numeral 28 denotes a temperature measurement cover which isdetachably fitted on the probe 16 and is constituted by a resin having alow thermal conductivity. A distal end portion 28a of the cover 28consists of a material through which infrared radiation can betransmitted.

FIG. 11 is an enlarged sectional view of the distal end portion of theprobe 16. The distal end portion 28a of the cover 28 covers the distalend portion of the probe 16 so as to prevent contact of the probe 16with the inner wall of the external ear canal.

FIG. 12 is a side view showing a state wherein the radiation clinicalthermometer 1 is stored in a storage case 30. The storage case 30comprises a mounting portion 30a for mounting the main body portion 10,and a storage portion 30b for storing the probe 16. A reflecting plate31 is fixed to a bottom surface 30c of the storage portion 30b at aposition corresponding to the distal end portion of the probe 16. Inaddition, a button depressing portion 30d is formed on the storage case30 at a position corresponding the check button 12. The storage case 30is used to perform an operation check of the radiation clinicalthermometer 1. When the thermometer 1 is set in the storage case 30 withthe power switch 13 being turned on as shown in FIG. 12, the distal endportion of the probe 16 is set on the reflecting plate 31, and at thesame time, the check buttom 12 is depressed by the button depressingportion 30d. This state is a function check state to be described later.In this state, a user can know from a display state of the display unit6 whether body temperature measurement can be performed.

FIG. 13 is a sectional view of an ear, showing a state wherein a bodytemperature measurement is performed by the radiation clinicalthermometer 1. Reference numeral 40 denotes a canal; 41, external earcanal; and 42, a drum membrane. A large number of downy hairs are grownfrom the inner wall of the external ear canal 41. Earwax is sometimesformed on the inner wall of the external ear canal 41. When the distalend portion of the probe 16 of the radiation clinical thermometer 1 isinserted in the external ear canal 41, and the major buttons 14 and 15are depressed with the distal end portion directed to the drum membrane42 as shown in FIG. 13, a body temperature measurement can beinstantaneously performed.

FIG. 14 is a block diagram of the radiation clinical thermometer 1 inFIG. 8. The same reference numerals in FIG. 14 denote the same parts asin FIG. 6, and a description thereof will be omitted.

Portions different from FIG. 6 will be described below. Referencenumeral 50 denotes a detection signal porocessing section. FIG. 14 showsa detailed arrangement of the section 50 corresponding to the amplifyingsection 4 shown in FIG. 6. More specifically, the section 50 comprisesan infrared amplifying circuit 51 for amplifying an infrared voltagev_(s) output from the infrared sensor 3a, a temperature-sensitiveamplifying circuit 52 for amplifying a temperatuyre-sensitive voltagev_(t) output from the temperature-sensitive sensor 3b, a peak holdcircuit 53 for holding a peak value of an output voltage V_(s) from theinfrared amplifying circuit 51, a switching circuit 54 for receiving theoutput voltage V_(s) from the infrared amplifying circuit 51 and anoutput voltage V_(sp) from the peak hold circuit 53 at input terminalsI₁ and I₂, respectively, and selectively outputting them from an outputterminal O in accodance with conditions provided from a control terminalC, an A/D converter 55 for converting the infrared voltages V_(s) orV_(sp) output from the switching circuit 54 into digital infrared dateV_(d), and an A/D converter 55 for converting the output voltage V_(t)from the temperature-sensitive amplifying circuit 52 into digitaltemperature-sensitive data T₀. With this arrangement, the section 50converts the infrared voltage v_(s) and the temperature-sensitivevoltage v_(t) supplied from the detecting section 3 into the digitalinfrared data V_(d) and temperature-sensitive data T₀, and outputs them.

An operating section 60 corresponds to the operating section 5 shown inFIG. 6, and comprises an emissivity input means 5a, a filter correctingmeans 5b, a body temperature operating circuit 61 corresponding to theoperating circuit 5c, a display driver 62 for receiving a bodytemperature data T_(b1) calculated by the operation circuit 61 anddisplaying it on a body temperature display portion 6a of a display unit6, a zero detector 63 for receiving the infrared data V_(d) output fromthe detection signal processing section 50 and outputting a detectionsignal S₀ when the infrared data V_(d) is detected to be zero so as toilluminate a measurement permission mark 6b of the display unit 6, asensitivity correcting calculator 64 for receiving thetemperature-sensitive data T₀ output from the section 50, calculating asensitivity R in accordance with equation (8) shown in FIG. 5, andoutputting it, and a sensitivity data input means 65 for outputting assensitivity data D a value which is externally input/set on the basis ofthe light-receiving area S of the infrared sensor 3a and the gain A ofthe infrared amplifying circuit 51 shown in equation (6).

Reference numeral 90 denotes a switch circuit to which a major switchSW_(m) operated by the major switches 14 and 15 shown in FIG. 8 and acheck switch SW_(c) operated by the check button 12 are connected. Wheneither of the major buttons 14 and 15 is depressed, the major switchSW_(m) is turned on, and a major signal S_(m) is output from a terminalM.

When the radiation clinical thermometer 1 is set in the storage case 30as shown in FIG. 12, the check button 12 is depressed, and the checkswitch SW_(e) is turned on. As a result, a check signal S_(c) is outputfrom a terminal C.

The major signal S_(m) output from the terminal M of the switch circuit90 is supplied to enable terminals E of the body termperature operatingcircuit 61 and the sensitivity correcting calculator 64. As a result,both the circuit 61 and the calculator 64 are set in an operative mode,and at the same time, the zero detector 63 is reset. The check signalS_(c) output from the terminal C of the switch circuit 90 is supplied toan enable terminal E of the zero detector 63, the control terminal C ofthe switching circuit 54, and a reset terminal R of the peak holdcircuit 53.

An operation of the radiation clinical thermometer 1 having theabove-described arrangement will be described below.

In an initial state wherein the power switch 13 of the radiationclinical thermometer 1 shown in FIG. 8 is turned on, since both thecheck switch SW_(c) and the major switch SW_(m) are kept off, the checksignal S_(c) and the major signal S_(m) are not output from the switchcircuit 70.

Consequently, in the operation section 60, the body temperatureoperating circuit 61 and the sensitivity correcting calculator 64 areset in a non-calculation mode, and the zero detector 63 is set in aninoperative mode. In addition, the switching circuit 54 of the detectionsignal processing section 50 selectively outputs the voltage V_(sp)input to the terminal I₂ to the output terminal O. The reset state ofthe peak hold circuit 53 is released and is set in an operative state.

The initial state is established in this manner. A function check modewill be described next.

When the thermometer 1 is set in the storage case 30 as shown in FIG.12, the check button 12 is urged against the button depressing portion30d of the storage case 50. As a result, the check switch SW_(c) shownin FIG. 14 is turned on, and at the same time, the distal end portion ofthe probe 16 is set at the position of the reflecting plate 31.

Consequently, the switch circuit 90 outputs the check signal S_(c) fromterminal C when the check switch SW_(c) is turned on, and supplies it tothe peak hold circuit 53, the switching circuit 54, and the zerodetector 63. Upon reception of the check signal S_(c), in the detectionsignal processing section 50, the peak hold circuit 53 is reset, and atthe same time, the switching circuit 54 is switched to a state whereinthe voltage V_(s) supplied to the input terminal I₁ is selectivelyoutput to the output terminal O. Subsequently, the A/D converter 55converts the infrared voltage V_(s) into a digital value and outputs itas the infrared data V_(d). In the operation section 60, the bodytemperature operating circuit 61 and the sensitivity correctingcalculator 64 are set in an inoperative mode, and only the zero detector63 is set in an operative state. The state of each portion in thefunction check mode has been described so far. The radiation clinicalthermometer 1 in this function check mode is operated as follows. Theinfrared data V_(d) obtained by converting infrared radiation reflectedby the reflecting plate 31 into a digital value by using the infraredsensor 3a, the infrared amplifying circuit 51, the switching circuit 54,and the A/D converter 55 is determined by the zero detector 63. If thisinfrared data V_(d) is zero, the zero detector 63 outputs the detectionsignal S₀ from the output terminal O so as to illuminate the measurementpermission mark 6b of the display unit 6.

The contents of the function check mode will be described below.

Referring to FIG. 10, as described above, since the infrared sensor 3a,the optical guide 20, and the hard cap 21 are connected to each otherthrough the metal housing 19 having a high thermal conductivity, thermalequilibrium of these components can be obtained. The above-describedfunction check mode is a mode for confirming that the thermalequilibrium is satisfactorily obtained. More specifically, infraredradiation energies emitted from the optical guide 20 and the hard cap 21each having the temperature T are reflected by the reflecting plate 31,and are incident on the infrared sensor 3a. In addition infraredradiation energy is emitted from the infrared sensor 3a having thetemperature T₀. The energy W obtained by subtracting the emitted energyfrom the incident energy is given by equation (5) as described above:

W═εσ(T₄ -T₀ ⁴)

If T═T₀, the energy W is not present. Hence, all the voltages v_(s) andV_(s), and the infrared data V_(d) are set to zero, and the detectionsignal S₀ is output from the zero detector 63. That is, the measurementready permission mark 6b is illuminated to confirm that the heat sourcecausing noise is present near the optical system 2, and hence bodytemperature measurement can be performed. Note that the zero detector 63determines the infrared data V_(d) as a digital value. A determinationvalue need not be strictly zero. The zero detector 63 outputs thedetection signal S₀ if the infrared date V_(d) is smaller than apredetermined determination value. In this case, even if the determinedvalue is not zero, it is regraded as negligible. If T≠T₀ according toequation 5, i.e., if there is a temperature difference among theinfrared sensor 3a, the optical guide 20, and the hard cap 21, thedifferential energy W is present. Therefore, the infrared data V_(d)becomes larger than the determination level of the zero detector 63. Asa result, the detection signal S₀ is not output, and the measurementpermission mark 6b is not illuminated.

In actual use of the radiation clinical thermometer 1, the state of T≠T₀occurs as follows.

When the environmental temperature in use of the radiation clinicalthermometer 1 is abruptly changed, the above state occurs. In this case,T≠T₀ occurs due to differences in heat capacity and responsecharacteristics of the respective elements. Since a measurement errorcorresponding to the value of the infrared data V_(d) based on thedifferential energy W occurs, the thermometer 1 is set in a measurementdisable state. In this state, if the thermometer 1 is left in a constantenvironmental temperature for a while, the respective elements arestabilized in a thermal equilibrium state upon thermal conductionthrough the metal housing 19, and the thermometer 1 is set in ameasurement permission state. However, it may takes several tens ofminutes to established such a stable state.

The function check mode has been described so far. A body temperaturemeasurement mode will be described next.

The radiation clinical thermometer 1 is detached from the storage case30 after illumination of the measurement permission mark 6b is confirmedin the above-described function check mode. When the thermometer 1 isdetached from the case, depression of the check button 12 is released,so that the check switch SW_(c) is turned off, and output of the checksignal S_(c) from the terminal C of the switch circuit 90 is stopped. Asa result, the reset state of the peak hold circuit 53 is released. Atthe same time, the switching circuit 54 is returned to the selectionstate for the input terminal I₂, and the zero detector 63 is returned tothe inoperative state.

Consequently, in the detection signal processing circuit 50, the peakvoltage V_(sp) of the infrared voltage V_(s) output from the infraredamplifying section 51, which is held by the peak hold circuit 53, issupplied to the A/D converter 55 through the switching circuit 54,thereby outputting the digital infrared data V_(d) converted from thepeak voltage V_(sp).

Although the zero detector 63 of the operating section 60 is returned tothe inoperative state, the measurement permission mark 6b of the displayunit 6 is kept illuminated because the detection signal S₀ is held by astorage circuit arranged in the zero detector 63. Since the major signalS_(m) is supplied to the reset terminal R, the detection signal S₀ ifthe zero detector 63 is maintained until the storage circuit is reset.

In this manner, the apparatus is prepared for measurement. When themajor buttons 14 and 15 are depressed after the radiation clinicalthermometer 1 is inserted in the external ear canal 41 in this state asshown in FIG. 13, a body temperature measurement is performed. Morespecifically, when the major buttons 14 and 15 are depressed, the majorswitch SW_(m) shown in FIG. 14 is turned on, and the major signal S_(m)is output from the terminal M of the switch circuit 90. As a result, inthe operation section 60, the body temperature operating circuit 61 andthe sensitivity correcting calculator 64 are set in an operative mode,and at the same time, the zero detector 63 is reset to turn off themeasurement permission mark 66 of the display unit 6. Infrared radiationenergy which is emitted from the drum membrane 42 and is incident on thethe probe 16 (the optical system 2 and the detection section 3 in FIG.14) inserted in the external ear canal 41 is converted into the infraredvoltage v_(s) by the infrared sensor 3a, and is amplified to the voltageV_(s) by the infrared amplifying circuit 51. Thereafter, the peakvoltage V_(sp) is held by the peak hold circuit 53. The peak voltageV_(sp) is converted into the infrared data V_(d) by the A/D converter55, and is supplied to the operating section 60. In addition, thetemperature-sensitive sensor 36 embedded in the metal housing 19 detectsthe temperature of the infrared sensor 3a and converts it into thetemperature-sensitive voltage v_(t). The voltage is converted into thetemperature-sensitive data T₀ by the A/D converter 56, and is thensupplied to the operation section 60.

When the infrared data V_(d) and the temperature-sensitive data T₀ aresupplied to the operation section 60, the sensitivity correctingcalculator 64 calculates the sensitivity R by using the data T₀ on thebasis of equation (8). Note that the coefficient of variation β is setto be -0.03. The body temperature operating circuit 61 then receives thesensitivity R calculated by the calculator 64, the sensitivity data Dfrom the sensitivity data input means, and the coefficient a of a termof degree 4 from the filter correcting means 5b, and calculates asensitivity coefficient K₃ of this system as K₃ ═aRD.

Upon reception of the calculated sensitivity coefficient K₃, theemissivity ε from the emissivity input means 5a, and the symmetricalaxis temperature b from the filter correcting means 5b, the bodytemperature operating circuit 61 performs a calculation based onequation (17):

    V.sub.d ═εK.sub.3 {(T.sub.b1 -b).sup.4 -(T.sub.0-b).sup.4 }(17)

Equation (17) is further rewritten to equation (18) so as to calculatethe body temperature data T_(b1). Since the external ear canal has auniform temperature, and the canal is regarded as a blackbody, theemissivity ε is set set as ε═1. ##EQU11## for b═45.95[K±]. Thus, thebody temperature data T_(b1) is displayed on a digit display portion 6aof the display unit 6 through the display driver 62.

One body temperature measurement is performed in this manner. Aprocedure of this operation will be described with reference to the flowchart of FIG. 15.

When the probe 16 is inserted in the external ear canal 41 (step 1),infrared radiation energy from the drum membrane 42 is converted intothe infrared voltage V_(s), and its peak voltage V_(sp) is held by thepeak hold circuit 53 (step 2). The presence/absence of the major signalS_(m) is then determined (step 3). If the major buttons 14 and 15 arenot depressed, NO is obtained in this step, and only the peak valueholding operation in step 2 is performed.

If the major buttons 14 and 15 are depressed, YES is obtaianed in step3. As a result, the zero detector 63 is reset by the major signal S_(m)(step 4). At the same time the sensitivity correcting calculator 64reads the temperature-sensitive data T₀ (step 5) and calculates thesensitivity R (step 6).

The body temperature operating circuit 61 reads the emissivity ε, thecoefficient a, the sensitivity R, and the sensitivity data D (step 7),and calculates the sensitivity coefficient K₃ by using the values a, R,and D (step 8). In addition, the operating circuit 61 reads thesymmetrical axis temperature b and at the peak-held infrared data V_(d)(step 9) and calculates the body temperature data step T_(b1) (step ○ 10). The display driver 62 receives the body temperature data T_(b1) anddisplays the body temperature on the display unit 6 (step ○ 11 ),thereby completing the body temperature measurement.

The function of the peak hold circuit 53 shown in FIG. 14 will bedescribed below with reference to FIG. 16.

FIG. 16 shows a temperature measurement curve of the radiation clinicalthermometer 1 of the present invention, which corresponds to thetemperature measurement curve of the conventional electronic clinicalthermometer shown in FIG. 1.

Temperature measurement time is plotted along the abscissa axis, andmeasurement temperatures are plotted along the ordinate axis. Theexternal ear canal 41 is a portion to be measured. A temperature curveH_(s) of the external ear canal 41 coincides with a measurementtemperature curve M_(s) of the radiation clinical thermometer 1. Asdescribe above, the downy hairs 43 and the earwax 44 are present in theexternal ear canal 41, as shown in FIG. 13. Similar to the drum membrane42, the downy hairs 43 and the earwax 44 are warmed to a temperaturevery close to a body temperature prior to the start of temperaturemeasurement. This state is indicated at time T₁ in FIG. 16. Morespecifically, time t₁ is the instant when the probe 16 is inserted inthe external ear canal 41. Since the temperature in the external earcanal 41 at this instant is substantially equal to the body temperatureT_(b1), infrared radiation energy having a body temperature level isincident on the infrared sensor 3a, and is stored in the peak holdcircuit 53 as the peak voltage V_(sp). However, the temperature in theexternal ear canal 41 is cooled by the probe 16 and quickly dropsimmediately after the probe 16 is inserted, as indicated by thetemperature curve H_(s). With this temperature drop, the infraredvoltage V_(s) detected by the infrared sensor 3a drops to the level ofthe temperature measurement curve M_(s), and hence cannot exceed thepeak voltage V_(sp). For this reason, the peak voltage V_(sp) at time t₁is stored in the peak hold circuit 53. It takes about 10 minutes for thelowered temperature represented by the curve H_(s) to return to theorigianl body temperature T_(b1). The reason will be described belowwith reference to FIG. 13.

When the probe 16 is inserted in the external ear canal 41, all thetemperatures of the drum membrane 42, each downy hair 43, and the earwax44 are decreased. Of these portions the temperature of the drum membrane42 can return to the level of the body temperature T_(b1) relativelyquickly because of the themal conduction from the body. However, sincethe thermal conduction from the body to each downy hair 43 and theearwax 44 having low degree of adhesion to the body is less, about 10minutes are required for their temperatures to return to the level ofthe body temperature T_(b1). Therefore, the temperature in the externalear canal 41 is set at the level of the body temperature T_(b1) only attime T₁, i.e., the instant when the probe 16 is inserted. Since theseries of operation processing of the radiation clinical thermometer 1cannot be performed by using the infrared radiation energy in such ashort period of time, the peak voltage V_(sp) appearing at the instantis stored in the peak hold circuit 53 as analog data, as indicated by adotted line in FIG. 16. The A/D conversion and the series of operatingprocessing are performed by using this stored peak voltage V_(sp),thereby performing the body temperature measurement.

Thus, in a radiation clinical thermometer without a preheating unit asin the present invention, the peak hold circuit 53 is indispensable. Byusing the peak hold circuit 53, the body temperature T_(b1) at time T₁can be measured within a very short period of time.

FIG. 17 a detailed arrangement of the peak hold circuit 53. The peakhold circuit 53 comprises an input buffer 80, an output buffer 81, adiode 82 for preventing a reverse current flow, a signal chargingcapacitor 83, and a switching transistor 84 for casuing the capacitor 83to discharge a charged voltage. The peak hold circuit 53 receives theinfrared voltage V_(s) and outputs its peak value as the peak voltageV_(sp). In addition, when the switching transistor 84 is turned on bythe check signal S_(c) supplied to the reset terminal R, the circuit 53causes the capacitor 83 to discharge a charged voltage.

FIG. 18 is a sectional view of a head portion 110 according to a thirdembodiment of the present invention. The same reference numerals in FIG.18 denote the same parts as in FIG. 10, and a description thereof willbe omitted.

The head portion in FIG. 18 differs from that in FIG. 10 in that athrough hole 19f is formed in a cylindrical portion 19a of a metalhousing 19 so as to expose an optical guide 20, and atemperature-sensitive sensor 3c is fixed to the exposed portion of theoptical guide 20. This temperature-sensitive sensor 3c is identical tothe temperature-sensitive sensor 3b, and is also fixed by a moldingresin.

The third embodiment differs from the second embodiment in a system forcorrecting thermal equilibrium in a probe 16. The second embodimentemploys the system of permitting measurement upon confirmation ofthermal equilbrium by the function check mode. In this system,measurement is inhibited while thermal equilibrium is not established.In contrast to this, the third embodiment comprises the twotemperature-sensitive sensors 3b and 3c to detect a temperturedifference between an infrared sensor 3a and the optical guide 20. Inthis system, if this temperature difference is excessively large,measurement is inhibited. If it is smaller than a predetermined value,body temperature measurement is permitted even though thermalequilibrium is not established. In this case, body temperature data iscalculated by adding a correction value based on the temperaturedifference to the measurement value, thus widening the range ofmeasurement conditions of the radiation clinical thermometer.

The circuit arrangement and operation of the radiation clinicalthermometer of the third embodiment will be described below withreference to FIG. 19. The same reference numerals in FIG. 19 denote thesame parts as in FIG. 14, and a description thereof will be omitted.

As shown in FIG. 18, a detecting section 3 comprises atemperature-sensitive sensor 3c for measuring a temperature T_(p) of theoptical guide 20. In the detection signal processing section 50, theswitching circuit 54 is omitted, and an output voltage V_(sp) from apeak hold circuit 53 is directly supplied to an A/C converter 55. Atemperature-sensitive amplifying circuit 57 and an A/D converter 58 areadditionally arranged in the section 50 so as to output the temperaturesensitive data T_(p).

In an operating section 60, an emissivity ε_(p) of the optical guide 20is set in an emissivity input means 5a, and a temperature differencedetector 67 is arranged in place of the zero detector 67 shown inFIG. 1. The temperature difference detector 67 receives temperature dataT₀ of the infrared sensor 3a detected by the two temperature-sensitivesensors 3b and 3c and the temperature data T_(p) of the optical guide20, and performs temperature difference determination with respect to apredetermined measurement limit temperature difference T_(d). If |T₀-T_(p) |<T_(d), i.e., the temperature difference is smaller than thelimit temperature difference, the detector 67 outputs a detection signalS₀ so as to illuminate a measurement permission mark 6b of a displayunit 6. This temperature difference determination is continued while thepower switch 13 shown in FIG. 9 is turned on. Therefore, the operationof the check button 12 as in the second embodiment is not required.

When the measurement permission mark 66 is illuminated, a bodytemperature measurement mode is set in the same manner as in the secondembodiment. However, the difference is that the temperature-sensitivedata T_(p) of the optical guide 20 is supplied to a body temperatureoperating circuit 61 in addition to the respective data described withreference to FIG. 14. In this embodiment, the circuit 61 calculates bodytemperature data T_(b2) in accordance with the following equation (19):##EQU12## where b═45.95[K] and ε_(p) ═0.05. This body temperature dataT_(b2) is obtained by correcting the temperature difference by thearithmetic operations described above, and is displayed on a bodytemperature display portion 6a of the display unit 6. Furthermore, inthis embodiment, a check signal S_(c) output from a switch circuit 90resets only the peak hold circuit 53. Therefore, when re-measurement ofa body temperature is to be performed, the peak hold circuit 53 must bereset first by operating the check button after illumination of themeasurement permission mark 6b is confirmed.

As described above, according to this embodiment, since body temperaturemeasurement can be performed without waiting for perfect thermalequilibrium of the respective elements of the probe 16, intervals ofrepetitive measurements can be reduced. In addition, since the functioncheck using infrared radiation is not required, a switching circuit anda storage case are not required so that the arrangement can besimplified.

In this embodiment, as an optimal embodiment, the arrangement whereinthe second temperature-sensitive sensor 3c is attached to the opticalguide 20 is shown. However, the present invention is not limited tothis. More specifically, the second temperature-sensitive sensor 3c isdesigned to detect the surface temperature of the optical guide 20 whichresponds to an ambient temperature more sensitively than the portion inwhich the temperature-sensitive sensor 3b is embedded. In considerationof the fact that the surface temperature of the optical guide 20 issubstantially equal to the ambient temperature, thetemperature-sensitive sensor 3c may be mounted on a circuit board onwhich a measurement IC chip is mounted as shown in FIG. 20 so as tomeasure an ambient temperature, so that the measured ambient temperatureis used as the surface temperature of the optical guide 20. Thisarrangement can also be satisfactorily used in practice.

As has been described above, according to the present invention, afilter correction value and a sensitivity correction value are suppliedto a body temperature operating circuit to calculate body temperaturedata, so that high measurement precision can be realized without using aheating unit as in the conventional thermometer, thus realizing acompact, low-cost radiation clinical thermometer which can be driven bya small battery and which can shorten a measurement time.

In addition, by employing a peak hold circuit for analog data in theradiation clinical thermometer, instantaneous measurement can beperformed, thus preventing a measurement disable state due to atemperature drop of a portion to be measured upon insertion of a probe.

Moreover, by employing a temperature difference correcting system usingtwo temperature-sensitive sensors, re-measurement intervals can beshortened, and the problem of thermal equilibrium of a probe, whichnarrows the range of measurement conditions of the radiation clinicalthermometer, can be solved. Therefore, the present invention is veryeffective to widely use a radiation clinical thermometer as a homethermometer, which has been used exclusively for a medical instrument.

What is claimed is:
 1. A radiation clinical thermometer comprising:aprobe including an optical system constituted by focusing means forfocusing infrared radiation from an object to be measured and a filterhaving transmission wavelength characteristics, an infrared sensor forconverting infrared radiation energy into an electrical signal, and atemperature-sensitive sensor for measuring a temperature of saidinfrared sensor and an ambient temperature thereof; detection signalprocessing means for receiving electrical signals from said infraredsensor and said temperature-sensitive sensor and outputting theelectrical signals as digital infrared data and temperature-sensitivedata, respectively; body temperature operating means for calculatingbody temperature data; and a display unit for displaying a bodytemperature in accordance with the body temperature data, includingfilter correcting means for setting a correction value based on thetransmission wavelength characteristics of said filter, wherein saidbody temperature operating means receives the infrared data, thetemperature-sensitive data, and the correction value from said filtercorrecting means so as to calculate body temperature data.
 2. Athermometer according to claim 1, further comprising sensitivitycorrection calculating means for receiving the temperature-sensitivedata and calculating sensitivity data of said infrared sensor, andwherein said body temperature operating means calculates the bodytemperature data by receiving the infrared data, thetemperature-sensitive data, the correction value from said filtercorrecting means, and the sensitivity data from said sensitivitycorrection calculating means.
 3. A thermometer according to claim 2,wherein said sensitivity correction calculating means calculatessensitivity data R according to the following equation:

    R═a{1+β (T.sub.0 -T.sub.m)}

where T₀ is sensitivity data of said temperature-sensitive sensor, T_(m)is a temperature at the time of sensitivity adjustment, α is asensitivity at the temperature T_(m), and β is a coefficient ofvariation of sensitivity.
 4. A thermometer according to claim 1, whereinsaid filter correcting means outputs a symmetrical axis, temperaturecorrection value which is used to change a symmetrical axis temperatureof a temperature-radiation energy characteristic curve represented by atemperature equation of a higher degree approximated to atemperature-radiation eneregy characteristic curve based on aStefan-Boltzmann law.
 5. A thermometer according to claim 1, whereinsaid probe comprises an optical guide for focusing infrared radiationenergy, a filter member arranged at one end of said optical guide,.[.an.]. infrared sensor arranged at the other end of said opticalguide, and .[.a.]. .Iadd.said .Iaddend.temperature-sensitive sensorarranged near said infrared sensor, said optical guide, said filtermember, said infrared sensor, and said temperature-sensitive sensorbeing coupled to each other by a metal housing having a high thermalconductivity.
 6. A thermometer according to claim 5, wherein said metalhousing is an integrally formed housing comprising a cylindrical portionin which said optical guide is inserted and a base portion formed at oneend of said cylindrical portion and having a storage recess for housingsaid infrared sensor and said temperature-sensitive sensor, said opticalguide being inserted and fixed in said cylindricl portion, said infraredsensor and said temperature-sensitive sensor being embedded in saidstorage recess of said base portion with a .[.molding.]. .Iadd.sealing.Iaddend.resin.
 7. A thermometer according to claim 5, furthercomprising a second temperature-sensitive sensor for detecting a surfacetemperature of said optical guide.
 8. A thermometer according to claim7, further comprising said second temperature-sensitive sensor arrangedon a surface of said optical guide in tight contact therewith.
 9. Athermometer according to claim 7, wherein said detection signalprocessing section comprises an A/D converter for converting anelectrical signal from said second temperature-sensitive sensor intosecond digital temperature-sensitive data, and said body temperatureoperating means calculates the body temperature data by using the secondtemperature-sensitive data as one of input signals.
 10. A thermometeraccording to claim 9, further comprising a temperature differencedetector for receiving the temperature-sensitive data from saidtemperature-sensitive sensor arranged at said base protion of said probeand the second temperature-sensitive data from said secondtemperature-sensitive sensor, and wherein said temperature differencedetector outputs a detection signal when a temperature difference isdetermined to be smaller than a predetermined measurement limittemperature difference.
 11. A thermometer according to claim 10, whereinsaid display unit comprises a measurement permission mark adapted to beilluminated by the detection signal output from said temperaturedifference detector.
 12. A radiation clinical thermometer comprising:aprobe including an optical means for focusing infrared radiation from anobject to be measured, an infrared sensor for converting infraredradiation energy into an electrical signal, and a temperature-sensitivesensor for measuring a temperature of said infrared sensor and anambient temperature thereof; detection signal processing means forreceiving electrical signals from said infrared sensor and saidtemperature-sensitive sensor and outputting the electrical signals asdigital infrared data and temperature-sensitive data, respectively; bodytemperature operating means for calculating body temperature data, and adisplay unit for displaying a body temperature in accordance with thebody temperature data, characterized by a zero detector for receivingthe infrared data output from said detection signal processing means anddetermining presence/absence of the infrared data, wherein said zerodetector outputs a detection signal when the infrared data is determinedto be zero or a small value.
 13. A thermometer according to claim 12,further comprising a storage case for storing said radiation clinicalthermometer and a reflecting plate arranged in said storage case at aposition corresponding to a probe end of said radiation clinicalthermometer stored in said storage case.
 14. A thermometer according toclaim 13, wherein said display unit comprises a measurement permissionmark adapted to be illuminated by the detection signal output from saidzero detector.
 15. A radiation clinical theremometer comprising:a probeincluding an optical means for focusing infrared radiation from anobject to be measured, an infrared sensor for converting infraredradiation energy into an electrical signal, and a temperature-sensitivesensor for measuring a temperature of said infrared sensor and anambient temperature thereof; detection signal processing means forreceiving electrical signals from said infrared sensor and saidtemperature-sensitive sensor and outputting the electrical signals asdigital infrared data and temperature-sensitive data, respectively; bodytemperature operating means for calculating body temperature data; and adisplay unit for displaying a body temperature in accordance with thebody temperature data, wherein said detection signal processing meansincludes a peak holding circuit for holding a peak value of theelectrical signal from said infrared sensor as analog data and an A/Dconverter for converting a peak value voltage held in said peak holdingcircuit into digital infrared data, and said body temperature operatingmeans calculates the body temperature data by using the infrared dataconverted from the peak value voltage; and wherein said probe l.[.including.]. .Iadd.includes .Iaddend.a filter having transmissionwavelength characteristics and wherein said display unit includes filtercorrecting means for setting a correction value based on thetransmission wavelength characteristics of said filter, wherein saidbody temperature operating means receives the infrared data, thetemperature-sensitive data, and the correction value from said filtercorrecting means so as to calculate body temperature data.
 16. Athermometer according to claim 15 wherein said filter correcting meansoutputs a symmetrical axis temperature correction value which is used tochange a symmetrical access temperature of a temperature-radiationenergy characteristic curve represented by a temperature equation of ahigher degree approximated to a temperature-radiation energycharacteristic curve based on Stefan-Boltzmann law.
 17. A thermometeraccording to claim 15 wherein said probe includes a filter havingtransmission wavelength characteristics and wherein said display unitincludes filter correcting means for setting a correction value based onthe transmission wavelength characteristics of said filter and furthercomprising sensitivity correction calculating means for receiving thetemperature-sensitive data and calculating sensitive data of saidinfra-red sensor and wherein said body temperature operating meanscalculates the body temperature data by receiving the infra-red data,the temperature-sensitive data, the correction value from said filtercorrecting means, and the sensitivity data from said sensitivitycorrection calculating means.
 18. A thermometer according to claim 17,wherein said sensitivity correction calculating means calculatessensitivity data R according to the following equation:

    R═a{1+β (T.sub.0 -T.sub.m)}

where T₀ is sensitivity data of said temperature-sensitive sensor, T_(m)is the temperature at the time of sensitivity adjustment, α is asensitivity at the temperature T_(m), and β is a coefficient ofvariation of sensitivity.
 19. A thermometer according to claim 15,wherein said optical means comprises an optical guide, a filter memberarranged at one end of said optical guide, said infrared sensor arrangedat the other end of said optical guide, .[.and.]. .Iadd.said .Iaddend.atemperature-sensitive sensor arranged near said infrared sensor, saidoptical guide, said filter member, said infrared sensor, and saidtemperature-sensitive sensor being coupled to each other by a metalhousing having a high thermal conductivity.
 20. A thermometer accordingto claim 19, wherein said metal housing is an integrally formed housingcomprising a cylindrical portion in which said optical guide is insertedand a base portion formed at one end of said cylindrical portion andhaving a storage recess for housing said infrared sensor and saidtemperature-sensitive sensor, said optical guide being inserted andfixed in said cylindrical portion, said infrared sensor and saidtemperature-sensitive sensor being embedded in said storage recess ofsaid base portion with a .[.molding.]. .Iadd.sealing .Iaddend.resin. 21.A thermometer according to claim 15, wherein said display unit includesa zero detector for receiving the infrared data output from saiddetection signal processing means and determining presence/absence ofthe infrared data, wherein said zero detector outputs a detection signalwhen the infrared data is determined to a zero of a small value.
 22. Athermometer according to claim 15, further comprising a storage case forstoring said radiation clinical thermometer and a reflecting platearranged in said storage case at a position corresponding to a probe endof said radiation clinical thermometer stored in said storage case. 23.A thermometer according to claim 22, wherein said display unit comprisesa zero detector and a measurement permission mark adapted to beilluminated by detection signal output from said zero detector.